If a beneficiary, 65 years or older, is enrolled in Medicare while he/she is still working and is also enrolled in their employer sponsored plan, the employer plan will be primary to Medicare, in many cases. In order for this statement to be true for the employee and/or 65 year old spouse, there has to be 20 or more employees, and the beneficiary must still be actively working.
If the employee (or spouse) is under the age of 65 and is enrolled in Medicare due to a disability, in order for the employer plan to be primary in this situation, there must be 100 or more employees. If the employer plan IS primary to Medicare, the beneficiary is able to delay Part B, or if already enrolled, could drop Part B, without incurring a penalty. While the employee is still working, he or she may sign up for Part B at any time. When the Beneficiary decides to end employment, they will then receive a Special Enrollment Period to enroll (or re-enroll) into Part B.
This Special Enrollment Period will last up to eight months after employment ends, or until the employer insurance ends, whichever comes first.